In this example we will see how a transformer can be used to change the voltage output of a wall receptacle. A friend returns from Europe with a device that she claims to be the world's greatest coffee maker. Unfortunately, it was designed to operate from a 240 V line, standard in Europe. At this rms voltage, the coffee draws 1500 W of power. (a) If your friend wants to operate the coffee maker in the United States, where the rms line voltage is 120 V, what turns ratio does her transformer need to have for the coffee maker to work

Explanation:

In order to use a device rated for use in 240 volt for use in 120 V , we have to use a step down transformer . In step down transformer no of turn in secondary coil is less than that in primary coil .

For transformer the relation is as follows

V₂ / V₁  = N₂ / N₁ = turn ratio

Where V₂ and V₁ are volts in secondary and primary coil and N₂ and N₁ is no of turns in secondary and primary coil.

Here V₂ = 120V , V₁ = 240 V

turn ratio = N₂ / N₁ = V₂ / V₁  = 120 / 240 = .5

turn ratio = .5 .

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explanation:

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